1. Field of the Invention
The present invention relates to a liquid crystal display device and a method for manufacturing the liquid crystal display device. More specifically, the invention relates to electronic equipment installed with an electro-optic device, which is typified by a liquid crystal display panel having circuits composed of thin film transistors (hereinafter, TFTs), and such electro-optic devices as components.
2. Related Art
In recent years, a technique for forming a TFT by a semiconductor thin film (having a thickness of approximately from several to several hundreds nm), which is formed over a substrate having an insulating surface. TFTs are applied broadly to electronic devices such as an IC or an electro-optic device, and has been rushed to be developed especially as a switching element of an image display device.
A liquid crystal display device has been known as an image display device. An active matrix liquid crystal display device becomes widely used since the active matrix liquid crystal display device is possible to provide high-resolution images compared with a passive liquid crystal display device. In an active matrix liquid crystal display device, an image pattern is formed on a screen by driving a pixel electrode arranged in a matrix configuration. In specific, a liquid crystal layer, which is interposed between a pixel electrode and an opposing electrode, is optically modulated by applying voltage between the pixel electrode, which is selected, and the opposing electrode, which corresponds to the pixel electrode. The optical modulation is recognized by an observer as a display pattern.
The range of usages of such active matrix electro-optical device becomes widen. The device is required to have high resolution, high opening ratio, and high reliability with the increasing of a screen size. Further, the productivity of the device is required to be improved, and the manufacturing cost is also required to be reduced.
The present applicant discloses drop of liquid crystal in U.S. Pat. No. 4,691,995.
It is an object of the present invention to provide a high reliable liquid crystal display device, which uses liquid crystal materials efficiently and which has flexibility.
Manufacturing cost is increased with the increasing of a panel size. Especially, the liquid crystal material interposed between a pixel electrode and an opposing electrode is expensive.
The invention provides a method for manufacturing a liquid crystal display device using a large substrate in size such as 320×400 mm, 370×470 mm, 550×650 mm, 600×720 mm, 680×880 mm, 1000×1200 mm, 1100×1250 mm, or 1150×1300 mm. Further, the invention provides a method for manufacturing a liquid crystal display device, which is suited to mass-production, using a large substrate in size such as 1500×1800 mm, 1800×2000 mm, 2000×2100 mm, 2200×2600 mm, or 2600×3100 mm.
In order to seal liquid crystal, a complex process such as drawing sealant, pasting an opposing substrate, dividing, injecting a liquid crystal, and sealing a liquid crystal inlet is required. Especially, in case of a large sized panel, it becomes difficult to inject a liquid crystal by a capillary phenomenon and to fill the region (at least including a pixel portion) surrounded by seal with the liquid crystal.
Two substrates are pasted together, and divided, and injected with the liquid crystal from a liquid crystal inlet formed on the divided surface. In this instance, a path extended from the liquid crystal inlet to a pixel region is filled with the liquid crystal. Further, in case of a driver circuit portion and a pixel portion are provided on one substrate, not only the pixel portion region but also the driver circuit region is sometimes filled with the liquid crystal. Except the region for display portion is filled with the liquid crystal.
There is the threat that since extremely larger amounts of liquid crystal passes the path of the liquid crystal extended from the liquid crystal inlet to the pixel region, especially, the vicinity of the liquid crystal inlet, compared with another region of the panel; the surface of an orientation film is deteriorated due to friction caused by injecting the liquid crystal, and a liquid crystal orientation is distorted as a result.
In addition, a liquid crystal display device is expected to be applied to various electronic equipment, especially a portable device. Presently, there are many liquid crystal display devices manufactured by using a glass substrate or a quartz substrate. However, these substrates have disadvantages of being fragile and heavy. Further, the glass substrate or the quartz substrate is unsuited to mass-production since it is difficult to use a large sized glass or quartz substrate for mass-production. Therefore it has been attempted that a substrate having flexibility, typically, a flexible plastic substrate is used for manufacturing a liquid crystal display device.
However, a plastic film has poor blocking properties against impurities such as moisture or alkaline metals, so that a high reliable liquid crystal display device cannot be obtained. Consequently, a liquid crystal display device having high technical advantages, which is manufactured by using a plastic substrate, has not been realized yet.